Freeserve/Wanadoo/Orange spam
Google “freeserve spam” or “wanadoo spam” and you’ll see these guys get themselves blacklisted frequently by dns blacklists for backscatter spam and for spammers using their network. Spamhaus, Spamcop and Sorbs all pick up some of their servers regularly. Their mails get bounced by any email provider using dns blacklists. Unfortunately, people keep using them. Why?
I’d write more on this, but so many have already.
If you’re attached to your Freeserve/Wanadoo/Orange account, but are sick of having your emails bounced, I suggest reading Andrew West’s Gmail workaround for Orange/Freeserve/Wanadoo customers with email problems.